You really need to speak to an attorney to get the best possible advice for your specific situation. There are ways to prove you have an ownership interest in the LLC. Even in the absence of an operating agreement, Pennsylvania law has a statutory scheme pertaining to the management of an LLC. It is possible to dissolve an LLC. These questions, and many more, arise in the context of a minority squeezeout, such as you have described. You should get an attorney to assist you in this complicated area.
If your partner has acted in a way that violates his fiduciary obligations to the company, he has violated PA laws. Even though you do not have an Operating Agreement, PA statutes provide for how the business is to be managed. You should immediately consult an attorney to protect your interests.
This response does not create an attorney-client relationship and is not intended to provide legal advice for your specific situation.
Wow. Go hire a lawyer PRONTO. I mean, no business relationship that begins with "we do not have an operat[ing] agreement" is going to be anything but a mess; those documents exist precisely to prevent these sorts of situations. Now, you're going to have to hire someone to run around trying to establish what is in whose name and who can assert what rights on behalf of the LLC.
Without reviewing a bunch of documents - some of which you apparently never drafted - I can't give you a good answer. I know this must be a terrifying situation for you; you're going to have to find a lawyer you can trust to work with you in ironing out this situation, because it just isn't going to resolve in any way you like, otherwise.
No information you obtain from this answer is legal advice, nor is it intended to be. You should consult an attorney for individualized advice regarding your situation. No attorney-client relationship is formed by my responding to your question.